BSIMSOI is a SPICE compact model for SOI (Silicon-On-Insulator) circuit design, created by University of California at Berkeley. This model is formulated on top of the BSIM3 framework. It shares the same basic equations with the bulk model so that the physical nature and smoothness of BSIM3v3 are retained. Four models are supported in ngspice, those based on BSIM3 and modeling fully depleted (FD, level 55), partially depleted (PD, level 57) and both (DD, level 56), as well as the modern BSIMSOI version 4 model (levels 10, 58). Detailed descriptions are beyond the scope of this manual, but see e.g. BSIMSOIv4.4 User Manual for a very extensive description of the recent model version. OpenMP support is available for levels 10, 58, version 4.4.